Collagen, the major structural protein in animals, comprises a family of more than ten genetically distinct proteins that are distributed among connective tissues in a specific and characteristic way. For example, Type I occurs in tendon and bone together with lesser amounts of several minor collagen types. cartilagenous tissues contain predominantly Type II collagen, together with a characteristics set of minor collagent types. In all of these tissues the collagen occurs in the form of fibrils, cylindrical bundles of triple-helical collagen molecules aligned parallel to the cylinder axis. However, the fibril morphology varies greatly from one tissue to another. The structure of Type I collagen has been extensively studied by x-ray diffraction, but Type II collagen has been inaccessible to this technique because of the small diameter of the fibrils and their lack of orientation in the tissue. Recently, however, it has been shown that the sheath of the lamprey notochord contains well oriented fibrils of Type II collagen that are capable of giving an excellent x-ray diffraction pattern. The diffraction data shows that the collagen in this tissue exists in a highly ordered crystalline array that is significantly different from the structure of Type I collagen. The objective of this proposal is to study the structure ot Type II collagen that exists in the fibrils of lamprey notochord sheath and the interactions of the fibrils with surrounding tissue components using both x-ray diffraction and electron microscopy. The study will be extended to determine whether this structure exists in other notochords, including those of higher vertebrates. Preliminary studies indicate that a mammalian Type II issues, the vitreous body of the eye, may share this same structure. Therefore, other sources of Type II collagen, including articular cartilage and nucleus pulposus will be examined to determine if these tissues also contain crystalline collagen. The structure of type II collagen is of interest because it is so different from the structure of Type I collagen and because of the fundamental place it occupies in embryogenesis and architecture of animals. In particular, Type II collagen is the major tensile component of articular cartilage and its destruction accompanies degenerative diseases such as arthritis. An understanding of Type II collagen structure will be of significance in developing therapies for this widespread malady.